natural structure definition
natural structure in p(x; y) means that most of the relevant information can be captured by a relatively compact representation. This in turn yields a normalized relevance-compression curve which is near unity even when I(T ;X) is small. On the opposite extreme, if any attempt to compress X loses a significant frac- tion of the relevant information about Y , the corresponding curve will be near the main diagonal of this plane. In the right panel of Figure 2.6 we illustrate these two cases. Note that analyzing joint distributions in the normalized relevance-compression plane must always be accompanied by considering the absolute information values.